The present invention generally relates to seed planting units using air pressure differential seed metering assemblies, and in particular, relates to a method and apparatus for selectively disconnecting an air pressure source from one or more seed metering assemblies.
Seed planting units generally include a laterally extending tool bar that supports a plurality of parallel planting units (also known as row units). The tool bar is typically coupled to a tractor or like vehicle suitable for towing the planting assembly along a field that is to be cultivated. Each planting unit includes a device for opening a furrow in the ground as the tractor draws the tool bar across a field to be seeded. Each planting unit further includes a seed meter to dispense seeds at a controlled rate into a seed furrow as the meter is advanced above and along the seed furrow during operation. One such seed metering assembly is described in U.S. Pat. No. 6,401,638 assigned to Case Corp., Racine, Wis., the disclosure of which is hereby incorporated by reference for the purpose of general background information. Generally seeds are delivered to the metering assembly from a seed hopper located on the planting unit or, alternatively, from a smaller container fed from a centralized large hopper used to feed all or a portion of the planting units. Each planting unit further includes a closing assembly that moves soil at the sides of the furrow to close the furrow over the planted seeds. Adjacent planting units are laterally spaced a sufficient distance to form furrows that are spaced a corresponding distance apart that is suitable for the type of seed being planted.
Air pressure differential seed meters, which are commonly known as air seed meters, are generally of two types, the first being a positive pressure type meter, and the second relying upon negative pressure or a vacuum. A positive pressure air seed metering mechanism includes a rotating disc defining apertures extending therethrough that are sized to retain one or more seeds to be planted. The metering mechanism is connected to an air mover that blows air into the seed chamber and onto the surface of the disc. The high pressure caused by the air mover creates a high pressure in the chamber that forces seeds from a seed mass into the apertures where they are retained for subsequent release into the furrow as the seed member rotates. In particular, the apertures open to atmosphere where the individual seeds are held by the blowing air until the seeds are dispensed by interrupting the flow of air to the seeds.
While positive pressure air seed meters offer certain advantages over conventional mechanical seed meters, they have certain limitations that need to be addressed during operation. In particular, a relatively high pressure differential must be applied to the disc in order to fill each hole or opening with the seed to ensure that a given furrow contains the appropriate number of seeds needed to produce a full yield. Accordingly, the seed hopper must be sealed to maintain pressure in the system. If for any reason the hopper lid comes off or the hopper otherwise becomes unsealed, the pressure differential at each planting unit will be reduced thereby jeopardizing reliable planting operation. Furthermore, the positive pressure is forced through the seed mass prior to engaging the apertures. Accordingly, the seed mass inhibits the efficiency of airflow into the meter.
Vacuum seed meters were therefore introduced to overcome some of the deficiencies in positive pressure seed meters and offer enhanced control over the seed being transported by the seed disc. In vacuum seed meters, a vacuum source is typically coupled to a separate chamber on the opposite side of the seed disc from the seed mass in the metering assembly. The vacuum pressure communicates through the apertures in the seed disc, and is sufficiently strong to draw the seed mass into the seed disc apertures. The seeds are held in the apertures until the disc rotates the seeds to the seed discharge area of the metering mechanism. The openings between the outer surface of the seeds and the periphery of the openings in the disc allows air to pass through, thereby maintaining the seeds in operable association with the disc. Because the pressure differential at the seed disc is provided by a vacuum source on the opposite side with respect with respect to the seed mass, and not from the flow of air at the same side as with positive pressure seed metering mechanisms, the difficulty of directing an air flow through the seed mass onto the seed disc is eliminated.
Regardless of the type of air seed meter being used, the total available air pressure usable in combination with the seed meter is limited by the air moving capacity of the air mover. It should be appreciated that the available air pressure available to each seed meter is thus a function of the quantity of metering assemblies included in the seed planting assembly. Typically, a second air mover is installed such that each air mover is responsible for delivering a pressure differential to a portion of the planting units in the assembly. It is common for thirty-one such planting units to be connected to the tool bar of a planting unit, such that fifteen planting are connected to a single air mover at a given time.
During a planting operation, the desired spacing between adjacent furrows can vary depending upon the type of seed being planted. In a typical arrangement, all thirty-one planting units are spaced along the toolbar at a sufficient distance to accommodate seeds that can be planted in narrowly spaced adjacent furrows to maximize the crop yield. Examples of such seeds include soybeans. Other types of seeds, such as corn, require that the distance between adjacent furrows be increased. The increased distance is typically accomplished by disengaging every other seed planting unit, thereby doubling the lateral distance between adjacent furrows that are created during operation.
Seed planting units can be disengaged, for example, by raising each unit upwardly about the tool bar and above ground level to prevent the planting unit from forming a furrow. The seeds are also removed from the hopper corresponding to that furrow or, if a centralized hopper is used, each raised planter can be operatively disconnected from the centralized hopper. It should thus be appreciated that a portion of the available air pressure for the metering assemblies would be wasted if permitted to travel into the metering assemblies of those planting units that have been raised. Because the limited supply of air pressure is valuable to enable reliable metering for those engaged planting units, it is desirable to redirect air pressure that would be used for disengaged planting units to those planting units that remain engaged during a planting operation.
Conventional seed planters use complicated valving that can be actuated to summarily block the passage of air pressure into every other seed planter that would be raised to increase the distance between adjacent furrows. The air is thus inherently redirected to those metering assemblies that remain operatively coupled to the air mover. Unfortunately, such valving assemblies are unnecessarily complex and expensive, and do not lend themselves suitable for modifying seed planters that have already been fabricated without the valving. Moreover, the valving does not enable the user to selectively determine which individual planting units are to be disengaged. Accordingly, if a planting unit is determined to be faulty, the user might not be able to include that planting unit among those to be raised and disconnected from the air mover.
What is therefore needed is a method and apparatus for selectively disconnecting individual planting units from the air mover for the purposes of disengaging the corresponding metering mechanism having less complexity and cost associated with fabrication of the apparatus. It would further be desirable to equip existing seed planters with the capability to selectively disengage planting units from the air mover.